Open heart surgery has been practiced for a number of years and the techniques for protection of the patient have been under study for all of this period. When the blood of the patient is by-passed to an extracorporeal support system which maintains the pumping function of the heart and the oxygenation function of the lungs, it is important that the heart itself be protected from ischemia, that is, deficiency of blood in the heart muscles, or, in other words, local anemia. In the circumstances of heart surgery, the possibility of damage to the heart is greatly reduced by cooling and administering drugs to the heart in a technique called "cardioplegia". A system for cooling the heart using the actual blood of the patient has also been developed and the use of blood as the vehicle for delivery of the cardioplegia has the advantage of keeping the heart oxygenated while it is arrested for the surgery.
Various methods for achieving cardioplegia have been used such as ice or slush baths with cooling coils submerged therein. Literature on the subject includes:
A Simple Method of Cold Coronary Perfusion Hillel Laks, M.D. et al--The Annals of Thoracic Surgery, Vol. 25, No. 4, Apr. 1978
Cold Cardioplegia Versus Hypothermia for Myocardial Protection. V. R. Conti, M. D. et al, The Journal of Thoracic and Cardiovascular Surgery, Vol. 76, No. 5, Nov. 1978
The present invention relates to an improved system for achieving cardioplegia which utilizes the life support equipment in a combined plan making it easier to control and administer the cold solutions and the drugs which are used in conjunction with the solutions. In previous techniques, the batch system has been used in which a quantity of the patient's blood is mixed with a quantity of medication in a single batch and then introduced into the patient's heart. From time to time, new batches might be requested by the attending surgeon and prepared and administered.
It is an object to provide a cardioplegic system which is more readily controlled and monitored along with the life support system itself and which enables the administration of the solution in a continuous fashion if desired as distinguished from the batch system. The blood pump itself can be used to monitor the cardioplegia flow rate and temperature monitoring is available immediately to an operator. In addition, the administration of drugs along with the cold solution has more reliability and reproducability in this system and apparatus to be disclosed and the mixing of the medication and blood can be achieved in a much more thorough manner than can be done in the batch system.
Thus, an overall consistency in administration can be achieved throughout an entire operation, which sometimes can extend for two or three hours, and also from one patient to another to obtain optimum results at all times.
Other objects and features of the invention will be apparent in the following description and claims in which the principles of the invention are set forth together with a detailed disclosure of the manner and process of using the invention directed to persons skilled in this art to enable the practice of the invention, all in connection with the best mode presently contemplated for the invention.